The invention resides in a fuel tank venting system specifically, a tank venting system for a vehicle with an internal combustion engine, wherein an absorption filter is disposed in a tank connecting line and a vent line with a regeneration valve extends from the absorption to an air intake duct of the engine.
DE 43 12 720 A1 discloses a tank venting system for a vehicle with an internal combustion engine which includes a tank communication line leading from the tank to an adsorption filter and a tank venting line, which includes a regeneration valve, and extends from the adsorption filter to an engine intake duct. This internal combustion engine includes a charger whereby, dependent on the adjustment of the pressure control valves, an excess pressure can be generated in the adsorption filter and the adsorption filter can be vented such that the fuel vapors are supplied to the intake duct.
This tank venting system has the disadvantage that it can be used only in connection with vehicles having an internal combustion engine with a charger wherein a part of the charge air flow is conducted into the adsorption filter. In addition, it is necessary that the line leading to the adsorption filter as well as the venting line extending from the adsorption filter includes expensive pressure control valves which have to be controlled by means of a pressure valve control apparatus. The arrangement further requires an additional communication line between the charger and the adsorption filter.
Tank venting arrangements are also known wherein the adsorption filter is regenerated utilizing the vacuum in the engine intake duct. These venting arrangements are usually utilized in connection with internal combustion engines which have no turbocharger. However, they have the disadvantage that the vacuum and consequently the reconditioning of the adsorption filter depends on the position of the throttle valve, that is, on the engine power output.
Under full engine load, there is essentially no vacuum in the engine intake duct because there is no throttling. In the full load range, in which the engine could accommodate the largest regeneration flow without effects on the emission values, the vacuum required for the regeneration is not available| During idling, however, when there is greatest vacuum in the engine intake duct, only small amounts of fuel vapors can be accommodated by the engine without detrimental effect on emission values.
It is the object of the present invention to provide a tank venting system for motor vehicles with internal combustion engines wherein a regeneration air flow proportional to the air mass intake flow into the engine is provided in a simple manner.